import java.util.LinkedList;
import java.util.Queue;

public class MyStackUseQueue {

    public Queue<Integer> qu1;
    public Queue<Integer> qu2;

    public MyStackUseQueue() {
        qu1 = new LinkedList<>();
        qu2 = new LinkedList<>();
    }

    public void push(int x) {
        if(!qu1.isEmpty()) {
            qu1.offer(x);
        }else if(!qu2.isEmpty()) {
            qu2.offer(x);
        }else {
            qu1.offer(x);
        }
    }

    public int pop() {
        if(empty()) {
            return -1;
        }
        if(!qu1.isEmpty()) {
            int size = qu1.size();
            for(int i = 0;i < size-1;i++) {
                qu2.offer( qu1.poll());
            }
            return qu1.poll();
        }else  {
            int size = qu2.size();
            for(int i = 0;i < size-1;i++) {
                qu1.offer( qu2.poll());
            }
            return qu2.poll();
        }
    }

    public int top() {
        if(empty()) {
            return -1;
        }
        if(!qu1.isEmpty()) {
            int size = qu1.size();
            int val = 0;
            for(int i = 0;i < size;i++) {
                val = qu1.poll();
                qu2.offer(val);
            }
            return val;
        }else  {
            int size = qu2.size();
            int val = 0;
            for(int i = 0;i < size;i++) {
                val = qu2.poll();
                qu1.offer(val);
            }
            return val;
        }
    }

    public boolean empty() {
        return qu1.isEmpty() && qu2.isEmpty();
    }
}
